1. Field of the Invention
The present invention relates to a light-emitting device, and more particularly, to an alternating current light-emitting device.
2. Description of the Prior Art
As optoelectronic technology develops, light emitting diode (LED) which is one of a variety of light sources is widely used in various fields and plays an important role in the optoelectronic industry. Typically driven by direct current (DC), a conventional LED chip has to operate in conjunction with a control circuit of alternating current to direct current conversion and a voltage reduction component in order to be used in a general living environment dominated by alternating current, thus incurring high manufacturing costs and compromising operation efficiency. Accordingly, it is necessary to develop a LED chip directly driven by alternating current. Since 2005, manufacturers based in the United States, Japan, South Korea and China have been disclosing light emitting diodes directly driven by alternating current (AC LED), indicating that LED AC is regarded as a new generation light-emitting device of great industrial potential.
Taiwanese Patent No. 200501464 and U.S. Pat. Nos. 6,547,249 and 6,957,899 taught a single-chip comprising two or multiple miniaturized light emitting diode dies such that the single-chip is operated under high-voltage alternating current. Similarly designed, the aforesaid patents each comprise at least one alternating current microdie light emitting diode module formed on a chip, the alternating current microdie light emitting diode module comprising at least two microdie light emitting diodes electrically connected to each other, and under alternating current the two microdies take turns to emit light in accordance with circuit connection direction.
The microdies have to be electrically independent of each other in order to take turns to emit light in accordance with different circuits. To achieve this, the microdies have to be spaced apart by a concave portion formed on the surface of the chip and between the microdies by means of etching or by any other means. However, electrical insulation of the microdies by the concave portion inevitably accompanies geometric separation of the microdies; as a result, fabricating a metal film between the microdies to achieve electrical connection is likely to decrease production yield.
Where the metal film is fabricated, by evaporation deposition or sputtering deposition, between the microdies to build an electrical connection path, step coverage of the metal film tends to be unsatisfactory because of a great bend at a corner or due to a vertical sidewall of the microdies, resulting in such problems as poor metal film attachment and uneven thickness of metal film. In consequence, open circuits arise for metal film discreteness. Also, surging metal film resistance compromises LED yield and even LED photoelectric conversion efficiency.
With the prior art being disadvantaged by undue open circuits, low yield, high resistance and inefficient photoelectric conversion, manufacturers nowadays are faced with an urgent issue, that is, an attempt to solve the aforesaid drawbacks of the prior art.